Tooth Development and Structure

Question 1

When are the first signs of tooth development in weeks?

Answer 1

6 weeks

Question 2

List the stages of tooth development.

Answer 2

1. Bud stage
2. Cap stage
3. Bell stage
4. Late bell/crown stage

Question 3

What are the 2 embryological tissue derivatives of dental tissue?

Answer 3

Ectoderm and mesenchyme

Question 4

What are the 3 stages in dentinogenesis?

Answer 4

1. Cytodifferentiation
2. Matrix formation
3. Mineralisation

Question 5

What occurs in matrix formation of dentinogenesis?

Answer 5

Odontoblasts produce predentine and then retreat inwards

Question 6

What forms the dentinal tubules?

Answer 6

The long cell processes of odontoblasts

Question 7

What cell form odontoblasts during cytodifferentiation?

Answer 7

Dental papilla cells

Question 8

Define amelogenesis.

Answer 8

Formation of enamel

Question 9

True or False: During amelogenesis, the enamel protein matrix secreted by ameloblasts takes a long time to mineralise.

Answer 9

False, mineralisation of enamel protein matrix is virtually immediate

Question 10

At what percentage of mineralisation is enamel considered ‘immature enamel’?

Answer 10

30%

Question 11

Why are deciduous teeth (baby teeth) whiter than adult teeth?

Answer 11

Enamel isn’t formed properly and is white as opposed to enamel that is formed to last a long period of time and is translucent, like on adult teeth

Question 12

What is the function of Hertwig’s epithelial root sheath?

Answer 12

Drive root development

Question 13

What percentage of enamel is inorganic?

Answer 13

96%

Question 14

Describe the amelodentinal junction.

Answer 14

The junction between the enamel and the dentine of a tooth.

Question 15

List the properties of enamel.

Answer 15

2mm thick
Hard but brittle
Translucent
Covers anatomical crown

Question 16

What is dentine?

Answer 16

A specialised C.T. consisting of 20% organic material like collagen that is strong and resilient and contains tubules

Question 17

What covers the root of a tooth?

Answer 17

A mineralised C.T. called cementum

Question 18

What property of cementum makes orthondontics possible?

Answer 18

Resistance to reabsorption

Question 19

Why is ground section histological examination better than a decalcified section?

Answer 19

Enamel is present

Question 20

What is the structure of enamel?

Answer 20

Prisms of tightly packed hydroxyapatite crystals in the core and then less tightly packed crystals in the sheath allowing for space for organic compounds

Question 21

What is the name for the incremental growth lines in enamel?

Answer 21

Striae of Retzius

Question 22

What are perikymata?

Answer 22

Shallow furrows where striae of Retzius reach the surface

Question 23

How do collagen fibres in dentine give strength?

Answer 23

Lie parallel to the amelodentinal junction

Question 24

What are the contents of dentinal tubules?

Answer 24

Cell processes
Nerves
Fluid

Question 25

Dentine is highly innervated. Where are most of the nerves located?

Answer 25

Pre-dentine and inner dentine in the pulp horns

Question 26

Describe the 3 types of dentine classifications.

Answer 26

1. Primary: during tooth development up to root completion 2. Secondary: After root completion 3. Tertiary: Response to pulpal insult

Question 27

True or False: Acellular cementum is found closer to the enamel while cellular cementum lies below the tooth root.

Answer 27

True

Question 28

What makes pulp different to connective tissue?

Answer 28

Specialised cells - odontoblasts Contained in a rigid chamber Blood vessels with no valves Densely innervated

Question 29

What are the layers of pulp from most peripheral?

Answer 29

1. Odontoblast layer 2. Cell-free zone of Weil 3. Cell rich zone 4. Pulp core

Question 30

What percentage of the pulpal innervation is unmyelinated?

Answer 30

70-80%

Question 31

What are the 2 sensations of myelinated fibres in the pulp?

Answer 31

Pain and pressure

Question 32

What is the plexus of Raschkow?

Answer 32

Section of pulp in the zone of Weil that monitors painful sensations

Question 33

Where is the marginal plexus found?

Answer 33

Around odontoblasts in the pulp